Virulence of entomopathogenic nematodes to pecan weevil larvae, Curculio caryae (Coleoptera : curculionidae), in the laboratory

The pecan weevil, Curculio caryae (Horn), is a key pest of pecans in the So utheast. Entomopathogenic nematodes have bct ll shown to be pathogenic towa rd the larval stage of this pest. Before this research, only three species of nematodes had been tested against pecan weevil larvae. In this study, th e virulence of the following nine species and 15 strains of nematodes towar d fourth-instar pecan weevil was tested: Heterorhabditis bacteriophora Poin ar (Baine, HP88, Oswego, NJ1, and Tf strains), H. indica Poinar, Karunakar & David (original and Homl strains),Il.,marelatus Liu & Berry (IN and Point Reyes strains), It megidis Poinar, Jackson & Klein (UK211 strain), II. zea landica Poinar (NZN3 strain), Steinernema riobrave Cabanillas, Poinar & Rau lston (355 strain), S. carpocapsae (Weiser) (All strain), S. feltiae (Filip jev) (SN strain), and S. glaseri (Steiner) (NJ43 strain). No significant di fference in virulence was detected among nematode species or strains. Nemat ode-induced mortality was not significantly greater than control mortality (in any of the experiments conducted) for the Following nematodes: E-I. bac teriophora (Baine), H. zealandica (NZH3), S. carpocapsae (All) S. feltiae ( SN), S. glaseri (NJ43), and S.,riobrave (355). All other nematodes caused g reater mortality than the control in at least one experiment. Heterorhabdit is megidis (UK211) but not II. indica (original) displayed a positive linea r relationship between nematode concentration and larval mortality. Results suggested that, as pecan weevil larvae age, they may have become mole resi stant to infection with entomopathogenic nematodes.